1. Field of the Invention
The invention relates to a camshaft support structure of an internal combustion engine.
2. Description of the Related Art
Technology is known which drives intake valves and exhaust valves by transmitting motion of a camshaft to the valves via rocker arms. Technology is also known in which a bearing portion on an upper side of a camshaft is provided on a head cover.
The rocker arms are first retained in predetermined positions by being sandwiched between the camshaft and the intake valves or the exhaust valves. Therefore, before the camshaft is assembled above the rocker arms, the rocker arms are unstable and may fall out of position when the camshaft is assembled above them. In particular, when assembling the head cover to the cylinder head after a bearing portion for the camshaft is provided on the head cover and the camshaft is assembled to the head cover, it is difficult to assemble the head cover while checking the state of each rocker arm, and the rocker arms tend to fall out of position when the head cover is being assembled. Moreover, if the rocker arms do fall out of position, they must be returned to the correct positions and the head cover then reassembled, which is troublesome.
In an attempt to solve this problem, Japanese Patent Application Publication No. JP-A-2003-155904 describes technology which inhibits rocker arms from falling out of position by providing a part that temporarily retains them. However, providing a part that temporarily retains the rocker arms increases the flow resistance of blowby gas. As a result, the flow velocity of the blowby gas increases such that oil is carried away with it. In addition, providing that part increases the total number of parts which increases the number of assembly processes, thereby raising manufacturing costs.